The present invention relates to the containment or recovery of gases and liquids erupting from a blown out oil well and more particularly to containment apparatus for use in an offshore environment to contain fluids erupting from a wellhead at the sea floor.
As the world wide demand for hydrocarbon fuels has increased, and known onshore reserves have not kept up with the demand, there has been increasing activity in offshore oil exploration and production. Reserves of oil known to exist in the offshore areas have steadily increased and an increasing percentage of world production is from these offshore areas. The offshore environment has presented numerous new challenges to the oil drilling industry which have been steadily overcome to allow efficient drilling and production in these areas although the costs has been considerably higher than that of onshore operations.
Not only has the offshore environment made production more difficult to accomplish, but it has also generally increased the risk of environmental damage in the event of a well blowout or other uncontrolled loss of hydrocarbons into the seas. As a result known safety equipment, such as blowout preventers which have been used successfully in onshore operations, has been used in the offshore operations also. In spite of the safety precautions, blowouts of offshore oil wells are known to occur and will occur again in the future.
While many of the techniques used in on shore operations to fight blowouts can also be applied in the offshore environment, they often prove to be less effective and require a much longer time period for implementation. Thus, for example, while relief wells can be drilled to intercept the blowout well, a great amount of time may be required in the drilling operation. In drilling the relief wells, platforms or other drilling support decks must be located and transported to the blowout site before drilling operations can be begun. Due to the rugged offshore environment, more time is required to drill the relief wells than would be required in an onshore operation. As a result of all of these difficulties, many months can pass between the occurrence of an offshore oil well blowout and the successful final capping of the blown out well. In the intervening time, large quantities of oil and gas can escape into the ocean with serious environmental impact.
While a portion of the hydrocarbons lost from a subsea well blowout may be trapped and skimmed up by various containment booms and oil skimmer ships, substantial quantities of hydrocarbons still escape such containment equipment. It can be seen that once the hydrocarbons are allowed to reach the ocean's surface, wave action tends to disperse the lighter hydrocarbons which may mix with water or evaporate into the air. The gaseous hydrocarbons of course tend to escape into the atmosphere. The heavier ends of the crude oil often form into globules or tarballs which may float at, or just below, the water's surface making it difficult to contain or skim up.
Natural oil seeps are known to occur from the sea floor in various parts of the world. Some of this oil has been recovered by placing heavy domes over the seep location and imbedding the lower edge or skirt of the dome in the sea floor sediments. When properly placed the dome prevents currents from carrying the seepage away and traps the seepage by simple gravity separation of oil and water. A small tubing is normally connected to the peak of the dome to allow occasional removal of collected oil. The dome structures are generally not suitable for containment of wellhead blowouts where large quantities of gas and oil are erupting. The force of such blowouts would tend to lift most domes. The dome shape is also not effective in diverting high speed flow. In the case of most blowouts large amounts of debris, such as drill pipe, casing, etc., fall to the sea floor around the wellhead. This debris makes it impossible to set any type of dome over the well head with any semblance of seal formed between the dome edges and the sea floor.
Thus, it can be seen that upon the occurence a offshore well blowout, it would be desirable to intercept and contain the erupting hydrocarbons as closely as possible to the wellhead and to direct then into processing equipment for separation and storage of the hydrocarbons.